The present invention relates to a computed tomography (CT) image production method and an X-ray CT system. More particularly, the present invention relates to a CT image production method and an X-ray CT system in which production of a large amount of data that is not actually used to construct a CT image can be avoided and a common procedure can be adapted to reconstruction planes whose positions relative to a multi-channel detector are different from one another.
One of the CT image production methods that have been known in the past is such that: real data that is acquired by detector arrays included in a multi-channel detector and that is contained in one of the views required for reconstruction of an image is projected onto a projection plane, which is a virtual plane, in a direction of X-ray transmission, and then interpolated or extrapolated on the projection plane in order to produce high-density data; data representing lines formed on a reconstruction plane with a space corresponding to a plurality of pixels between adjoining lines is sampled from the high-density data, and then interpolated or extrapolated on the reconstruction plane in order to produce interlinear data; and the foregoing processing is repeated in order to summate data items, which are produced from all the views required for reconstruction of an image on the reconstruction plane, pixel by pixel for the purpose of constructing a CT image (refer to, for example, Patent Document 1).
[Patent Document 1] Japanese Unexamined Patent Application Publication No. 2003-334188
Assume that a plurality of reconstruction planes whose positions relative to a multi-channel detector are different from one another is designated. The foregoing conventional CT image production method has the advantage that a procedure starting with sampling of data, which represents lines formed on a reconstruction plane with a space corresponding to a plurality of pixels between adjoining lines, from high-density data and ending with construction of a CT image can be adapted in common irrespective of the relative positions of reconstruction planes.
However, since a large amount of data that is not actually used to construct a CT image is produced on a projection plane, a processing time is too long.
In contrast, according to another CT image production method, real data that is acquired by detector arrays included in a multi-channel detector and that contained in one of the views required for reconstruction of an image is projected onto a reconstruction plane in a direction of X-ray transmission in order to produce linear data. The linear data is interpolated or extrapolated on the reconstruction plane, whereby data is produced on the reconstruction plane. This processing is repeated, and resultant data items produced from all the views, which are required for reconstruction of an image, on the reconstruction plane in order to construct a CT image.
According to the CT image production method, production of a large amount of data, which is not actually used to construct a CT image, on a projection plane can be avoided.
However, since the position of linear data is different among a plurality of reconstruction planes whose positions relative to a multi-channel detector are different from one another, a procedure starting with production of linear data and ending with construction of a CT image must be programmed for each of the reconstruction planes.